Mackie Musical Instrument U420 User Manual

4-Channel Line Mixer with FireWire  
O W N E R ’ S M A N U A L  
1
2
3
4
LEVEL  
SET  
LEVEL  
SET  
U
U
U
U
GAIN  
GAIN  
POWER  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
U
U
U
U
U
U
U
U
U
U
U
U
EQ  
EQ  
HIGH  
HIGH  
L
R
OL  
10  
7
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
MID  
MID  
4
0
4
10  
20  
LOW  
LOW  
AUX  
AUX  
O O  
FW IN  
O O  
PHONES  
MAX  
MAX  
O O  
O O  
O O  
O O  
U
U
U
U
LEVEL  
LEVEL  
LOOP  
OUT  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
O O  
MAX  
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Contents  
IMPORTANT SAFETY INSTRUCTIONS ........................ 2  
INTRODUCTION ...................................................... 4  
FEATURES............................................................... 4  
GETTING STARTED................................................... 5  
HOOKUP DIAGRAMS............................................... 6  
21. FW LOOP OUT......................................... 14  
SOFTWARE INSTALLATION..................................... 24  
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Part No. SW0556 Rev. D 02/08  
©2007-2008 LOUD Technologies Inc. All Rights Reserved.  
Owner’s Manual  
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FEATURES  
Introduction  
4 stereo line-level input channels.  
Built-in FireWire 2x2 interface provides easy  
input from computer to the main mix, and easy  
outputs to the computer from the main mix. It  
has 24-bit resolution, and 44.1, 48, 88.2, and 96  
kHz sample rates.  
Thank you for choosing a Mackie U.420 mixer. It  
contains all your favorite features in a ultra-compact  
4-channel line mixer, along with a built-in FireWire  
interface, and a phono input for turntablists.  
The U.420 is equally at home in recording studio ap-  
plications or in live performances:  
Separate FireWire modes for live performance  
or overdubbing.  
In the studio, the mixer offers Mackie-quality sound  
to sub-mix outboard gear and bring it into the computer.  
It has 4 stereo inputs that can accept any stereo device  
from synths, samplers, or a turntable. Channel 1 accepts  
an instrument connection without the need for a DI box.  
Ultra-compact design, with functional and  
ergonomic controls.  
3-Band EQ on each channel, with kill position.  
Phono preamplifier on channel 4 accepts  
phono-level stereo signals from a turntable.  
In live performances, the mixer will enable you to  
sub-mix synths, computers, samplers, pedal boards,  
turntables, cd-players, and effects on stage. Bands  
and solo artists from DJs, electronic artists and singer  
songwriters can use the mixer to sub-mix their creative  
tools and deliver them to the sound board. The mixer’s  
aux bus allows you to set up a separate mix to feed stage  
monitors or external processors.  
Instrument-level input option on channel 1.  
Stereo aux bus allows a separate mix to be sent  
to stage monitors or external processors.  
TRS stereo main outputs.  
TRS stereo headphone output.  
TRS stereo aux bus outputs.  
Level-set LEDs and gain controls allow easy  
optimization of each channel.  
You will find that the U.420 mixer is a very useful  
piece of equipment, and we hope you will love it, just as  
much as we did making it for you.  
Stereo main meters with overload lights.  
Large, easy to use, main level control.  
External power supply.  
Includes Tracktion, our professional, easy-to-  
use, totally-amazing music production software.  
HOW TO USE THIS MANUAL  
Please read the safety instructions on page 2 first.  
The getting started guide on page 5 will help you get the  
mixer set up fast so you can start using it right away.  
Right after that are the ever popular hook-up diagrams  
that show you some typical setups.  
The features section describes every knob, button,  
and connection point on the mixer, roughly following  
the signal flow through the mixer from top to bottom.  
For more information about a feature, locate its number  
in the appropriate illustration, and find it in the nearby  
paragraphs.  
Please write your serial number here for future  
reference (i.e., insurance claims, tech support,  
return authorization, etc.)  
This icon marks information that is critically  
important or unique to the mixer. For your  
own good, read them and remember them.  
This icon leads you to in-depth explanations  
of features and practical tips. They usually  
have some valuable nuggets of information.  
Purchased at:  
Appendix A shows service and repair information.  
Appendix B is a section on connectors.  
Appendix C shows the specs and a block diagram.  
Appendix D shows details of the FireWire interface.  
Date of purchase:  
4
U.4ꢀ0 4-Channel Line Mixer  
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Set the Levels  
Getting Started  
To set the gain controls, it’s not even necessary to  
hear what you’re doing at the outputs of the mixer. If  
you want to listen while you work, plug headphones into  
the phones jack on the front panel, then set the phones  
knob up a little.  
READ THIS PAGE!!  
Even if you never read manuals, please  
read and digest the safety instructions  
on page 2, and this page before you  
begin using your mixer.  
1. Play something into the selected input. Be sure  
that the volume of the input source is the same as  
it would be during normal use. If it isn’t, you might  
have to readjust these levels during the middle of a  
set.  
Zero the Controls  
1. Unplug the mixer’s external power supply from the  
mixer.  
2. Adjust the channel’s rotary gain control so that the  
level set LED comes on while you are playing, and  
goes off when you stop. As a rough guide, adjust the  
gain until the LED is on for about half the time dur-  
ing your performance. (The LED indicates that the  
signal level is 0 dBu.)  
2. Turn down all the gain, aux, and level controls, and  
center all the EQ controls.  
3. Set all push button switches to their “out” positions.  
3. Repeat for any other channels.  
4. In the center section, turn down the large level  
knob, FW in knob, and phones level knob.  
Instant Mixing  
Connections  
1. To get sound out of the speakers, turn up the  
channel’s level control to the U (unity gain) position,  
and slowly rotate the large main control to a comfort-  
able listening level.  
If you already know how you want to connect the  
mixer, go ahead and connect the inputs and outputs  
the way you want them. If you just want to get sound  
through the mixer, follow these steps:  
2. Sing and play. You’re a star! Bring in the other  
channels, and generally have fun.  
1. Plug a signal source into the mixer. This could be a:  
3. Grease the frying pan with hog fat and turn up the  
heat just enough to not fill the kitchen with fine  
blue smoke.  
Turntable into the phono input.  
Line-level source such as a CD player into a  
line-level input.  
4. Cook the sausages until golden brown, and serve  
with black pudding and a pint of warm beer.  
A guitar plugged into channel 1’s left input,  
with the instrument switch pressed in.  
2.  
Connect cords from the main outs to your powered  
speakers or amplifier.  
FireWire  
3. Plug in the mixer’s external power supply, and con-  
nect it to a live AC outlet to turn on the mixer.  
1. See Appendix D, on page 21 for details of getting  
started with FireWire.  
4. If you have powered speakers, turn them on. Other-  
wise, hook up your speakers to your amp and turn it  
on. Adjust your powered speaker or amplifier level  
controls to however the manufacturer recommends.  
(This is usually all the way up.)  
2. There is a nice section about recording with  
FireWire on page 22.  
3. There is no step 3. Well, only this one, and it is not  
very informative. (Tech writers just love numbered  
lists.)  
4. There is no step 4 either.  
Other Nuggets of Wisdom  
Always turn down the main level control and phone  
level control before making any connections.  
When you shut down your equipment, turn off the  
amplifiers first. When powering up, turn on the  
amplifiers last.  
5
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Hookup Diagrams  
HR824  
Powered  
Monitors  
Drum machine  
Effects/ Sampler  
Headphones  
MAIN  
OUT  
AUX  
OUT  
L
L
MONO)  
L
(MONO)  
ONO)  
(MONO)  
3
2
1
GN
ONO  
POWER  
18V,1.5A  
R
R
R
R
R
ground wire  
Laptop  
Keyboard  
Turntable with phono-level out  
This diagram shows a stereo synth, and a drum machine connected to channels 1 & 2, and a turntable  
connected to the phono inputs of channel 4. The stereo aux output sends signals to the effects/sampler,  
and the wet signal is returned into channel 3.  
The main outputs are fed to a pair of Mackie HR studio monitors for control room listening, and the  
mixers Big Knob controls their volume. The headphone out has its own level control, independent of the  
Big Knob.  
A laptop is connected via FireWire. The U.420 provides stereo mains to the computer for record-  
ing with most DAW applications like Tracktion, Cubase, or Sonar. This is independent of the Big Knob  
as well. Additionally, there is a stereo return from the laptop that has its own mix level control into the  
mains.  
The FireWire loop through switch on the top of the mixer makes overdubbing a breeze. In its normal  
out position, you can play back the mix from your DAW and it will not create a feedback loop. Only the  
analog inputs 1-4 will be available for recording. Track it!  
Oh, and don’t forget this FireWire return can be used for any playback software application like  
Ableton Live, Tracktor, or iTunes.  
Production studio  
U.4ꢀ0 4-Channel Line Mixer  
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SRM450  
Powered  
Speakers  
Guitar  
SRM450 Powered  
Stage Monitor  
Drum machine  
Headphones  
MAIN  
OUT  
AUX  
OUT  
L
L
L
(MONO
ONO)  
L
(MONO
(MONO)  
4
3
2
1
GN
PHONO  
L
POWER  
18V,1.5A  
R
R
R
R
R
ground wire  
Laptop  
Keyboard  
Turntable with phono-level out  
This diagram shows a guitar connected to channel 1, plus a stereo synth and drum machine connected  
to channels 2 & 3. A turntable is connected to the phono inputs on channel 4. Use the left aux send to  
connect to a Mackie SRM450 for stage monitoring. The U.420 will automatically sum the stereo signal to  
mono if you use the left aux output only.  
The main outputs are fed to a pair of Mackie SRM450s for the audiences listening pleasure. The  
mixers Big Knob controls their volume. The headphone out has its own level control, independent of the  
Big Knob.  
A laptop is connected via FireWire. The U.420 provides stereo mains to the computer for recording  
with most DAW applications like Tracktion, Cubase or Sonar. Perfect for recording your set. Any play-  
back software applications like Ableton Live or Tracktor can easily be part of your performance by utiliz-  
ing the FireWire stereo return that has its own mix level control into the mains.  
The FireWire loop through switch on the top of the mixer allows you to send your FireWire return  
through the FireWire output for recording. So use Ableton Live and your analog inputs to perform, and  
record it all at the same time on Tracktion or your DAW of choice. The switch should be pressed in to  
allow loop through of the FireWire return to the FireWire record output.  
Live performance system  
7
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Personal Stereo Monitors  
(SRM150 powered monitors)  
This diagram shows an acoustic  
guitar connected to channel 1, plus  
a stereo performance synth like a  
Nord Lead on channel 2, a good  
organ like a Korg CX-3 on chan-  
nel 3, and an electronic piano on  
channel 4 (with a dab of chanel #5  
behind each ear for good measure).  
Acoustic  
Guitar  
Main Mix  
to  
front-of-house  
mixer  
Electronic Piano  
The main outputs are fed to the  
FOH (front of house) mixer for the  
audiences listening pleasure. The  
stereo aux output is being sent to a  
pair of SRM150s on mic stands for  
stereo stage monitoring.  
MAIN  
OUT  
AUX  
OUT  
L
L
MONO)  
L
(MONO)  
L
(MONO)  
(MONO)  
4
3
2
1
GN
ONO  
POWER  
18V,1.5A  
R
R
R
R
R
A laptop is connected via  
FireWire. This laptop is loaded with  
awesome virtual instruments like  
those in applications such as Logic,  
and a USB keyboard is connected  
for real-time performance.  
Organ  
Nord Lead  
Keyboard Controller  
Laptop  
Keyboardist’s submixer  
This diagram shows a stereo keyboard  
workstation, a groovy analog synth, an  
electronic piano, and an electric organ con-  
nected to channels 1–4.  
HR824  
studio  
monitors  
Electronic Piano  
Aux to  
studio mixer  
The main outputs are fed to a pair of  
Mackie HR studio monitors for local monitor-  
ing, and the mixers Big Knob controls their  
volume. The headphone output has its own  
level control, independent of the Big Knob.  
The stereo aux out sends signals to the main  
studio recording console for tracking.  
MAIN  
AUX  
OUT  
OUT  
L
L
(MONO)  
L
(MONO)  
L
(MONO)  
O)  
4
3
2
1
GND  
PHONO  
L
POWER  
18V,1.5A  
R
R
R
R
R
R
A laptop is connected via FireWire. This  
laptop is loaded with awesome virtual  
instruments like those in applications such as  
Logic, and a USB keyboard is connected for  
real-time performance and recording.  
Laptop  
The FireWire loop through switch on top  
of the mixer makes overdubbing a breeze.  
In its normal out position, you can playback  
the mix from your DAW and it will not  
create a feedback loop. Only the analog  
inputs 1-4 will be available for recording.  
Track it!  
Headphones  
Rhodes  
Keyboard Controller  
Analog Synth  
Keyboard workstation  
Keyboard recording station  
8
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DigitalVideo  
Camcorder  
HR824  
Powered  
Monitors  
Headphones  
MAIN  
OUT  
AUX  
OUT  
L
L
L
(MONO)  
L
(MONO)  
L
(MON
(MONO)  
4
3
2
GN
PHONO  
L
POWER  
18V,1.5A  
R
R
R
R
R
R
Video out  
DV Recorder 1  
Video out  
iPodTM Docking Station  
Desktop computer and large display  
DV Recorder 2  
Video Monitor  
This diagram shows a DV camcorder audio connected to channel 1, DVR decks connected to channels  
2 and 3, and an iPod docking station connected to channel 4.  
The main outputs are fed to a pair of Mackie HR studio monitors for local monitoring, and the mixers  
Big Knob controls their volume. The headphone output has its own level control, independent of the Big  
Knob.  
A Mac with a cinema display is connected via FireWire to the mixer. The computer audio comes from  
a video production application like Final Cut Pro for monitoring during editing. The audio inputs can also  
be recorded through the mixers FireWire connection.  
Video edit bay  
9
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Rear Panel Features  
MAIN  
OUT  
AUX  
OUT  
L
L
L
(MONO)  
L
(MONO)  
L
(MONO)  
(MONO)  
4
3
2
1
GND  
PHONO  
L
POWER  
18V,1.5A  
R
R
R
R
R
R
ꢁ. PHONO Inputs  
1. INSTRUMENT/LINE Input  
Channel 4’s RCA jacks accept stereo phono-level  
signals from turntables. Check that your turntable has  
a phono-level output and a moving-magnet cartridge.  
Turntables usually have a ground wire that needs to be  
connected to the ground terminal [4].  
These inputs accept either 1/4" TRS balanced or TS  
unbalanced connectors.  
Unlike the other inputs, channel 1’s left input can  
accept direct instrument-level signals such as from  
guitars, without the need for a DI box. For this to work,  
press channel 1’s instrument switch [11]. The guitar or  
other instrument will appear on both left and right of  
channel 1. (The right input is disconnected internally.)  
The turntable’s stereo phono-level signals are re-  
equalized and converted to line-level signals by the fine  
RIAA preamplifiers inside the mixer.  
The phono inputs are internally disconnected  
if anything is plugged into channel 4’s line  
inputs.  
If the instrument switch is out, then these inputs are  
just like the other channel line-level inputs described  
below.  
Do not connect line-level sources to these  
phono-level inputs, or the phono preamplifiers  
may be overloaded. Use the line-level inputs  
[2] instead.  
ꢀ. LINE Inputs  
These line-level inputs accept either 1/4" TRS bal-  
anced or TS unbalanced connectors.  
You can connect stereo line-level sources such as CD  
players, MP3 players, keyboards, drum machines, tape  
players, and all manner of line-level goodies. You might  
need to purchase some RCA to 1/4" mono adapters, de-  
pending upon your source component. These are readily  
available at your local music, electronics, or grain and  
feed store.  
4. GND Terminal  
This terminal is provided to connect a ground wire  
from your turntable to the mixer. Most turntables pro-  
vide a ground wire for the purpose of eliminating hum in  
the audio signals.  
Rotate this terminal counter-clockwise to loosen it,  
wrap the end of the ground wire clockwise around the  
terminal, and hand-tighten the terminal for a secure  
ground connection.  
These are stereo inputs; the left signals appear on the  
left main mix bus, and the right signals appear on the  
right main mix bus.  
If you have a mono source component, then connect  
it to the left input, and the mono source will appear  
equally on the left and right of the main mix. (This does  
not apply to channel 4.)  
5. AUX Outputs  
These 1/4" TRS jacks provide a balanced line-level  
output signal from the stereo aux bus. Use these to  
connect to the inputs of an external effects processor,  
another PA system, or stage monitors. You can also use  
unbalanced 1/4" TS connectors.  
10  
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If you plug a cable into the left aux output  
jack, and leave the right output jack empty,  
the right and left signals are summed together  
Warning: The headphone amp is designed to  
drive any standard headphones to a very loud  
level. We’re not kidding! It can cause perma-  
to provide a mono output.  
nent hearing damage. Even intermediate levels may be  
painfully loud with some headphones. Be careful!  
The stereo aux output from these connectors is the  
sum of all channels whose aux level controls [16] are  
set to more than minimum. The aux bus gives you the  
chance to make a second mix or send an individual  
channel from the mixer, independent of the main level  
control [23] or channel level controls [17].  
Always start with the phones level control turned all  
the way down before connecting headphones or making  
any connections. Keep it down until you’ve put on the  
headphones, and turn it down whenever you play a new  
source.  
You could use the aux output to feed stage monitors,  
or to feed a headphone amplifier so you can wear head-  
phones on stage. This lets you get a different mix than  
the audience is hearing, plus you get to look a lot cooler  
and surprisingly attractive with headphones on.  
8. DC Input  
This DC input connector is used to supply power to  
the mixer. Connect the supplied external power supply  
here, and plug the other end of the power supply into  
the AC mains. The power LED [18] will joyfully illumi-  
nate, indicating that the mixer is powered on, and ready  
for some super fun.  
If you are going out to an external processor, you can  
return its processed output to one of the mixer’s line-  
level input channels.  
The universal external power supply that comes with  
your mixer can accept any AC voltage from 100 VAC to  
240 VAC.  
ꢂ. MAIN OUTs  
These 1/4" TRS connectors provide stereo line-  
level signals from the main mix. Connect these to  
the balanced inputs of the active speakers, or power  
amplifier(s) powering your main speakers.  
9. FIREWIRE Connection  
FireWire (IEEE 1394) is a high-speed serial I/O inter-  
face for connecting digital devices. The mixer has one  
FireWire connector for transferring digital audio to and  
from your computer.  
The main mix is the sum of all active channels cur-  
rently playing, including any 2 channel FireWire input.  
How much of a channel that is heard in the main mix, is  
determined by that channel’s level control [17].  
The FireWire interface provides two audio outputs to  
your computer:  
If you plug a cable into the left output jack,  
and leave the right output jack empty, the  
right and left signals are summed together to  
provide a mono output.  
Main mix output, left and right. These output  
signals are independent of any adjustments  
made to the main level control [23]. This al-  
lows you to easily record your live performance  
directly to your laptop.  
Balanced 1/4" TRS connections offer better  
immunity to external noise (specifically, hum  
and buzz) than 1/4" TS unbalanced con-  
The FireWire loop out switch [21] lets you  
choose if you want the FireWire input to be  
connected to the FireWire output for recording.  
See page 15 for more details of this switch.  
nections. Because of this, it is the preferred  
interconnect method, especially in cases where very  
long lengths of cable are being used. A long unbalanced  
cable carries with it more opportunity for noise to get  
into the system — having balanced cables means very  
little noise will enter the system. If you must use an  
unbalanced connection, keep the cable length to 10 feet  
or less (3 meters).  
The FireWire interface also lets you use your com-  
puter to play back two channels into the mixer:  
Left and right signals from your computer are  
added to the main mix. The FW in control [20]  
allows you to adjust the level of the incoming  
audio being added to the main mix.  
7. HEADPHONES Output  
See Appendix D on page 21 for more FireWire details,  
and the block diagram on page 20.  
This 1/4" TRS stereo jack is where you plug in your  
stereo headphones.  
The headphone volume is controlled by the phones  
level control [22]. It is not affected by the main level  
control [23].  
The headphones output is the main mix, taken just  
before the main level control [23].  
11  
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Top Panel Features  
1
2
3
4
LEVEL  
SET  
LEVEL  
SET  
U
U
U
U
GAIN  
GAIN  
POWER  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
U
U
U
U
U
U
U
U
U
U
U
U
E
EQ  
HIGH  
HIGH  
L
R
OL  
10  
7
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
MID  
MID  
4
0
4
10  
20  
LOW  
LOW  
AUX  
AUX  
O O  
FW IN  
O O  
PHONES  
MAX  
MAX  
O O  
O O  
O O  
O O  
U
U
U
U
LEVEL  
LEVEL  
LOOP  
OUT  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
O O  
MAX  
When this switch is out, input 1 is a line-level input,  
Channel Controls  
just like inputs 2–4. You can connect stereo line-level  
sources such as CD players, MP3 players, keyboards,  
drum machines, and tape players. You will need a DI  
box if connecting instrument-level signals to the inputs  
when this switch is out.  
10. LEVEL SET LED  
These LEDs are used with the gain control [12] to set  
the level of the channel’s preamplifier gain just right.  
They light when the signal level is 0 dBu.  
1ꢀ. GAIN  
Adjust the gain control so these LEDs come on while  
you are playing, and go off when you stop. As a rough  
guide, adjust the gain until the LEDs are on for about  
half the time during your performance.  
These knobs allow you to adjust the gain of each  
channel’s stereo preamplifier.  
Signals from the line-level input jacks go straight  
to the preamplifiers. Phono-level signals entering the  
phono inputs [3] of channel 4 are first passed through  
an RIAA phono preamplifier to become line-level signals.  
Setting the gain correctly will ensure that the pre-  
amplifier’s gain is not too high, where distortion could  
occur, and not too low, where your quieter, exquisitely-  
delicate passages might be lost in background noise.  
The gain ranges from –14 dB to +14 dB, and the  
center U position represents unity, or zero gain. Adjust  
the gain so the level set LEDs [10] come on while you  
are playing, and go off when you stop. As a rough guide,  
adjust the gain until the LED is on for about half the  
time during your performance. Listen for any distortion  
at the higher levels.  
11. INSTRUMENT SWITCH  
When this switch is pressed in, channel 1’s left input  
can accept direct instrument-level signals from guitars  
or other instruments. They will be impedance-matched  
to the channel 1 left input, without the need for a DI  
box. (The right input is disconnected.)  
Adjust the gain after plugging in any input, or playing  
a new source or instrument for the first time.  
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ꢁ-BAND EQ  
1ꢂ. AUX  
The U.420 has 3-band equalization at carefully  
selected points — low shelving at 300 Hz, mid peaking  
at 1 kHz, and high shelving at 4 kHz. “Shelving” means  
These stereo controls allow you to adjust how much of  
the channel signal is added to the aux bus. The aux bus  
contains the sum of all channels whose aux controls are  
that the circuitry boosts or cuts all frequencies past the set to more than minimum.  
specified frequency. For example, rotating the low EQ  
The aux bus feeds the aux outputs [5], typically out  
knob clockwise will boost the bass at 300 Hz and below.  
“Peaking” means that certain frequencies form a “hill”  
around the center frequency — 1 kHz in the case of the  
mid EQ.  
to an external processor. Each channel’s stereo signal  
retains it’s stereo image as it is sent to the aux bus.  
This is great for keyboard players who work with stereo  
sounds from stereo effects processors.  
Be careful with the EQ, or you can really upset  
things. We’ve designed a lot of boost and cut  
into each equalizer circuit, because we know  
A look at the block diagram may shed some  
light on the aux signal path, but you can skip  
this part if you like. The following diagram  
shows just one channel, but each channel  
everyone will occasionally need that. But if  
you max the EQs on every channel, you’ll get mix mush.  
Equalize subtly and use the left sides of the knobs  
(cut), as well as the right (boost). You can create many  
interesting and useful EQ changes by turning the knobs  
down and adjusting the level [17] up if needed.  
adds to the aux bus and main bus in the same way.  
Level Set  
3-Band EQ  
L
Gain  
Level  
LO  
HI  
MID  
R
LO MID  
HI  
If all the EQ controls in a channel are turned down to  
the kill position, then that channel is effectively muted.  
(Word: DJs find it very useful to have EQ controls with a  
kill position, in their fast-paced beat-based world.)  
Aux Out L  
L
R
Aux  
1ꢁ. HIGH EQ  
Aux  
Sum  
Aux Out R  
This gives up to 10 dB of boost for the frequency range  
above 4 kHz, and the highs are muted in the kill posi-  
tion. In the center position U, high EQ has no effect.  
The channel signals go through the preamplifier and  
into the EQ. The level control [17] allows you to adjust  
how much of the channel appears on the main mix bus.  
The aux control [16] allows you to adjust how much of  
each channel appears on the aux bus.  
Use it to add sizzle to cymbals, and an overall sense  
of transparency, or edge to keyboards, vocals, guitar and  
bacon frying. Turn it down a little to reduce sibilance, or  
to hide tape hiss.  
The aux output is affected by the gain, EQ, and  
aux level of each channel.  
The aux output is not affected by the level  
control of each channel, and it is independent  
of the main mix bus.  
14. MID EQ  
This gives up to 10 dB of boost for frequencies cen-  
tered around 1 kHz, and the mid range is muted in the  
kill position. In the center position U, mid EQ has no  
effect.  
For an example, you could set up a stage monitor for  
the guitar player. Connect an amplifier or a powered  
monitor to the aux outputs [5]. Set all aux level con-  
trols to minimum, then turn up the guitar channel’s aux  
level to suit. Any adjustments of the level [17] or main  
level [23] will not affect the stage monitor level, so your  
guitar player will be happy, and that is always a good  
thing. Mark that one on your calender as a special day.  
Midrange EQ is often thought of as the most dynamic,  
because the frequencies that define any particular  
sound are almost always found in this range.  
15. LOW EQ  
17. LEVEL  
This gives up to 10 dB of boost for the frequency range  
below 300 Hz, and the lows are muted in the kill posi-  
tion. In the center position U, low EQ has no effect.  
These level controls allow you to adjust how much of  
the channel signals appear on the main mix bus. They  
have no effect on the level of signals going onto the  
aux bus. Adjust these carefully to acheive a nice blend  
in your main system and headphones. Turn down any  
unused channels.  
The frequency range below 300 Hz represents the  
realm of bass drums, bass guitar, fat synth patches, and  
lower down to some really serious male singers.  
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1
2
3
4
LEVEL  
SET  
LEVEL  
SET  
U
U
U
U
GAIN  
GAIN  
POWER  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
U
U
U
U
U
U
U
U
U
U
U
U
E
EQ  
HIGH  
HIGH  
L
R
OL  
10  
7
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
MID  
MID  
4
0
4
10  
20  
LOW  
LOW  
AUX  
AUX  
O O  
FW IN  
O O  
PHONES  
MAX  
MAX  
O O  
O O  
O O  
O O  
U
U
U
U
LEVEL  
LEVEL  
LOOP  
OUT  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
O O  
MAX  
Control Section  
18. POWER LED  
ꢀ0. FW IN  
This will light whenever the external power supply is  
connected to the mixer and to a live AC mains supply.  
The mixer does not have a power switch, so as long as  
the external power supply is connected and operating,  
this LED should be on.  
This control lets you adjust the signal level of the two  
FireWire channels coming in from your computer, rela-  
tive to the mix of channels 1 to 4. Adjust it carefully to  
achieve the desired mix with the other channels. (If the  
other level controls [17] are down, then the meters will  
show the level of the FireWire input only.)  
19. METERS  
The FireWire input from your audio software such as  
Tracktion, could be individual instrument tracks, a mix  
of tracks, or processed tracks.  
These meters have 8 LEDs each, ranging from –20 to  
+13.5 (OL). They indicate the stereo signal strength of  
the main mix after the main level control [23].  
Typically, you want to see these meters bouncing  
between the “0” and the “+4” LEDs. It is okay if the OL  
LEDs light occasionally, but if they light frequently or  
continuously, turn down the main level control until  
they blink occasionally or not at all.  
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ꢀ1. FW LOOP OUT  
ꢀꢁ. MAIN LEVEL  
In addition to a mix of channels 1 to 4, the FireWire  
This big handy knob adjusts the main mix output level  
output to the computer can contain any FireWire input, at the main outputs [6]. Use it wisely to turn up the  
if this switch is down. (The mains and phones are not  
affected by the switch, and always provide a full mix of  
channels 1 to 4 and the 2-channel FireWire inputs.)  
tunes in your main speakers, or to turn it down when-  
ever you think the room could benefit from a little less  
noise from your band.  
If disengaged (out), the FireWire output to  
your computer will just be the main mix from  
channels 1 to 4. This is a good position for  
overdubbing, as any playback from your com-  
puter can be played in your main speakers and  
headphones, while you play along with a guitar  
and record only the guitar via FireWire.  
The meters will also be affected by this control. It  
does not adjust the levels to your headphones, FireWire  
outputs, or the aux outputs.  
ꢀ4. FAIRY DUST  
Sometimes, all you need is a little bit of  
fairy dust to make your recording climb to  
number 1 in the charts. If you really-really  
believe in this imaginary control, adjust it  
carefully to sprinkle golden fairy dust throughout your  
recording session. Fame and fortune are just a wing beat  
away.  
1
2
3
4
U
U
U
U
LEVEL  
LEVEL  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
FireWire recording channels 1–4 only  
If pressed in, the FireWire output to your  
computer will be the mix of channels 1 to 4,  
including any FireWire audio coming in from  
your computer. This is a good position to record  
live, where your complete main performance  
(including any input from the computer) can  
be recorded via FireWire.  
1
2
3
4
U
U
U
U
LEVEL  
LEVEL  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
FireWire input from computer  
LOOP  
OUT  
O O  
FW IN  
MAX  
PRESS IN TO MAKE THIS CONNECTION  
FireWire recording channels 1–4 and FireWire in  
ꢀꢀ. PHONES LEVEL  
This controls the volume of the headphones output  
from off to maximum gain.  
Warning: The headphone amplifier is de-  
signed to drive any standard headphones to a  
very loud level. It can cause permanent hear-  
ing damage. Even intermediate levels may be painfully  
loud with some headphones. Be careful! Always start  
with the phones level control turned all the way down  
before connecting headphones or making any connec-  
tions. Keep it down until you’ve put on the headphones,  
and turn it down first whenever you play a new source or  
instrument.  
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Appendix A: Service Information  
If you think your U.420 has a problem, please check  
out the following troubleshooting tips and do your best  
to confirm the problem. Visit the Support section of our  
lots of useful information such as FAQs, documentation,  
and user forums. You may find the answer to the prob-  
lem without having to send your U.420 away.  
If you are playing a guitar into channel 2, 3, or 4,  
you need to use a DI box for the correct impedance  
match and high frequency fidelity.  
Try the same source signal in another channel, set  
up exactly like the suspect channel.  
Only phono-level sources (turntables) should be  
connected to the RCA phono inputs [3]. The phono  
section requires your cartridge to be a moving-mag-  
net type. It may be too low to amplify the low levels  
of a moving-coil type.  
Troubleshooting  
No Power  
If there is no phono output, check that there is  
nothing plugged into channel 4’s line inputs. The  
phono inputs are internally disconnected if any-  
thing is plugged into channel 4’s line inputs.  
Make sure the external power supply is securely  
seated in the DC input [8] and plugged all the way  
into the AC outlet.  
Only line-level sources should be connected to the  
line-level inputs [2] of channels 2, 3, and 4.  
Make sure the AC outlet is live (check with a tester  
or lamp).  
If possible, listen to the signal with headphones  
plugged into the input source device. If it sounds  
bad there, it’s not the mixer causing the problem.  
Is the power LED [18] illuminated? If not, make  
sure the AC outlet is live.  
Are all the lights out in your town? If so, contact  
your local power company to get power restored.  
Bad Output  
If no LEDs are illuminated, and you are certain  
that the external power supply is working, it will be  
necessary to have your mixer serviced. There are no  
user serviceable parts inside. Refer to “Repair” on the  
next page to find out how to proceed.  
Is the associated level control (if any) turned up?  
If a left output is presumed dead, switch the left  
and right cords at the mixer end. If the problem  
stays on the left side, it’s not the mixer. but maybe  
your left speaker, left speaker cables, or left ampli-  
fier channel.  
Bad Channel  
Check the connections from your source are made  
securely, and that the cords are in good condition.  
Noise/Hum  
Check that your turntable’s audio ground wire is  
Check the channel’s program gain controls [12] are  
set correctly.  
connected to the ground terminals [4].  
Turn down each channel, one by one. If the noise  
disappears, it’s coming from whatever is plugged  
into that channel. Check your whatever.  
Are that channel’s EQ controls all turned down to  
the kill position perchance?  
Is the signal source turned up? Make sure the  
signal level from the selected input source is high  
enough to light the level set LEDs [10] when ad-  
justed with the gain controls.  
Check the signal cables between the input sources  
and the mixer. Disconnect them one by one. When  
the noise goes away, you’ll know which input source  
is causing the problem.  
If you are playing a guitar or other instrument level  
source into channel 1, make sure the instrument  
switch [11] is engaged.  
It helps to plug all the audio equipment into the  
same AC circuit so they share a common ground.  
If the annoying humming continues, ask the drum-  
mer to leave the room, or at least have him learn  
the words.  
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Repair  
For warranty repair or replacement, refer to the war-  
ranty information on page 27.  
Non-warranty repair for Mackie products is available  
at a factory-authorized service center. To locate your  
nearest service center, visit www.mackie.com, click  
“Support” and select “Locate a Service Center.” Service  
for Mackie products living outside the United States can  
be obtained through local dealers or distributors.  
If you do not have access to our website, you can call  
our Tech Support department at 1-800-898-3211,  
Monday-Friday, 7 am to 5 pm Pacific Time, to explain the  
problem. Tech Support will tell you where the nearest  
factory-authorized service center is located in your area.  
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Appendix B: Connections  
1/4" TRS Phone Plugs and Jacks RCA Plugs and Jacks  
“TRS” stands for Tip-Ring-Sleeve, the three connection  
RCA-type plugs (also known as phono plugs) and jacks  
points available on a stereo 1/4  
jack or plug. TRS jacks and plugs are used for balanced  
signals and stereo headphones:  
"
or balanced phone  
are often used in home stereo and video equipment and  
in many other applications. They are unbalanced and  
electrically equivalent to a 1/4 TS phone plug.  
"
TIP  
SLEEVE TIP SLEEVE  
Balanced Mono  
RING SLEEVE  
TIP  
SLEEVE RING TIP  
RCA Unbalanced Wiring:  
Sleeve = Shield  
Tip = Hot (+)  
RING  
TIP  
SLEEVE  
1/4 TRS Balanced Mono Wiring:  
"
Sleeve = Shield  
Tip = Hot (+)  
Ring = Cold (–)  
Stereo Headphones  
RING SLEEVE  
TIP  
SLEEVE RING TIP  
RING  
TIP  
SLEEVE  
1/4 TRS Stereo Unbalanced Wiring:  
"
Sleeve = Shield  
Tip = Left  
Ring = Right  
1/4" TS Phone Plugs and Jacks  
“TS” stands for Tip-Sleeve, the two connection points  
available on a mono 1/4  
"
phone jack or plug. They are  
used for unbalanced signals.  
SLEEVE  
SLEEVE  
TIP  
TIP  
TIP  
Dimensions  
SLEEVE  
8.8 in/  
3.4 in/  
224 mm  
87 mm  
1/4 TS Unbalanced Wiring:  
"
Sleeve = Shield  
Tip = Hot (+)  
WEIGHT  
2.5 lb  
1.13 kg  
8.6 in/  
218 mm  
18  
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Appendix C: Technical Info  
Specifications  
Frequency Response (ꢀ0 Hz to ꢀ0 kHz, unity gain) :  
Input Impedance:  
Line input:  
Line input to any output:  
+0/–0.5 dB  
100 kΩ balanced  
Phono input to any output:  
0.5 dB of RIAA EQ  
curve  
Phono input:  
47.5 kΩ shunt with 200 pF  
Maximum Output Levels:  
Main out:  
FireWire output to FireWire input  
(with loop out switch engaged):  
+15 dBu  
+0/–0.5 dB  
Aux out:  
+15 dBu  
Distortion (THD+N):  
Main and aux output, 20 Hz to 20 kHz, 1 kHz input signal:  
Phones:  
1.5 Vrms into 32 Ω (70 mW)  
Output Impedance:  
Main out:  
Line input at unity gain, 4 dBu input signal:  
Better than 0.008%  
120 Ω  
120 Ω  
50 Ω  
Phono input at unity gain, –30 dBu input signal:  
Better than 0.030%  
Aux out:  
Phones:  
FireWire output to FireWire input : Better than 0.005%  
Equalization  
Low:  
Phones output, 20 Hz to 20 kHz, +4 dBu input signal:  
Line input at unity gain:  
Better than 0.004%  
+10/–inf dB @ 300 Hz  
+10/–inf dB @ 1 kHz  
+10/–inf dB @ 4 kHz  
Mid:  
Attenuation/Crosstalk:  
High:  
Main level at unity gain, 1 kHz input signal placed on any chan-  
nel with gain knob at unity and level knob at minimum,  
main outs (20 Hz–20 kHz):  
FireWire  
Sample rates:  
44.1 kHz, 48 kHz,  
88.2 kHz, 96 kHz  
Better than –85 dBu  
Main level at unity gain, 1 kHz input signal placed on any chan-  
nel with gain knob at unity and level knob at minimum, main  
outs measured (20 Hz to 20 kHz) with any other channel gain  
knob at unity and level knob at unity:  
Resolution:  
24-bit  
VU Meters  
8–segment post main level meters  
Better than –85 dBu  
OL (+13), +10, +7, +4, +0, –4, –10, –20 dBu  
Noise Characteristics:  
Signal to Noise Ratio, 20 Hz to 20 kHz, ref +4 dBu:  
Level set LED (sensitivity):  
0 dBu  
Main out at unity, all channel gain knobs at minimum:  
Better than –91 dB  
AC Power Requirements:  
Power consumption:  
8.3 watts  
Main out at unity, all channel gain knobs at unity (dummy plugs  
in channel 4 TRS inputs so phono is disengaged):  
Better than –86 dB  
Universal AC power supply:  
100–240 VAC, 50–60 Hz  
Physical Dimensions and Weight:  
Main out at unity, channels 1 – 3 at minimum, channel 4 phono  
at unity gain (no TRS plugs in channel 4):  
Better than –74 dB  
Height:  
Width:  
Depth:  
Weight:  
8.6 in/218 mm  
8.8 in/224 mm  
3.4 in/87 mm  
2.5 lb/1.13 kg  
All channel aux knobs at unity and all channel gain knobs at  
unity:  
Main out at unity, all channel gain knobs at minimum, FireWire  
input level at unity: Better than –87 dB  
Better than –89 dB  
LOUD Technologies Inc. is always boldly striving to improve  
our products by incorporating new and improved materi-  
als, components, and manufacturing methods. Therefore, we  
reserve the right to change these specifications at any time  
without notice.  
Maximum Input Levels (rated at 1% THD):  
Line inputs, unity gain:  
+15 dBu  
Phono input:  
77 mV rms @ 1kHz  
“Mackie,” and the “Running Man” are registered trademarks of  
LOUD Technologies Inc. All other brand names mentioned are  
trademarks or registered trademarks of their respective hold-  
ers, and are hereby acknowledged.  
Input/Output Characteristics:  
Input gain control range:  
Line input gain knob:  
Line input level knob:  
Output gain control range:  
Main level knob:  
–14 to +14 dB  
Off to +10 dB  
©2007-2008 LOUD Technologies Inc. All Rights Reserved.  
Off to +10 dB  
Off to +10 dB  
Channel aux knob:  
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R x u A  
L x u A  
R
R x u A  
L x u A  
R
n i a M  
n i a M  
L
L
ꢀ0  
U.4ꢀ0 4-Channel Line Mixer  
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Appendix D: FireWire  
FireWire stream to computer  
System Requirements  
In addition to a mix of channels 1 to 4, the FireWire  
output to the computer can contain any FireWire input  
from your computer, if the FW loop out switch [21] is  
down.  
These are the minimum requirements for your com-  
puter system to use the U.420 FireWire interface.  
For the PC:  
Windows XP (service pack 2)  
Pentium 4 or Athlon XP processor  
256 MB RAM  
1
2
3
4
U
U
U
U
LEVEL  
LEVEL  
O O  
O O  
O O  
O O  
MAX  
MAX  
MAX  
MAX  
FireWire input from computer  
For the Mac:  
OS X (10.3.9 or higher)  
LOOP  
OUT  
O O  
MAX  
FW IN  
G4 processor  
256 MB RAM  
PRESS IN TO MAKE THIS CONNECTION  
The mains and phones outputs are not af-  
fected by the switch, and always provide a  
full mix of channels 1 to 4 and the 2-channel  
The internal FireWire interface will allow the left and  
right main mix to be recorded on a Mac or PC computer.  
It also allows two channels of audio to be added to the  
main mix from the computer.  
FireWire input.  
The analog audio from the mixer is converted to digi-  
tal signals by the FireWire interface’s A/D converters.  
FireWire stream from computer  
The following table shows the outputs to your com-  
puter from the FireWire interface:  
The following table shows the outputs from your com-  
puter to the mixer’s FireWire interface:  
To  
From  
From  
To  
Computer input 1 Left mix of channels 1 to 4  
with FW input (switch down)  
Computer output 1 Main mix L  
Computer output 2 Main mix R  
or without FW in (switch up)  
Computer input 2 Right mix of channels 1 to 4  
with FW input (switch down)  
The 2-channel digital stream from the computer  
enters the mixer through the FireWire connector and is  
converted to analog audio.  
or without FW in (switch up)  
Here are two examples of using the FW loop out  
switch:  
The audio level can be adjusted using the FW in  
control [20].  
Studio Overdub – Tracktion playback is coming  
into the mixer on FireWire inputs, and routing  
through the mains/phones for you to hear. A  
guitar plugged into channel 1 is being recorded  
via the FireWire output, while you listen and  
play along to the Tracktion playback. The FW  
loop switch is up, so the FireWire output to the  
computer contains all playing channels except  
the FireWire playback.  
Beware of a possible feedback loop, if you are  
feeding the main mix back into the mixer.  
Live Performance – Computer playback software  
like Ableton Live is being mixed to the mains  
with other stereo sources such as synths, sam-  
plers, turntables, and CD-DJ players. The FW  
loop switch is down, so everything will be fed to  
the FireWire out for recording an entire set.  
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Direct hardware monitoring  
Recording with FireWire  
The U.420’s built in FireWire connection allows over-  
dub style recording to a Mac or PC digital audio work-  
station (DAW) through the FireWire cable.  
When in performance or “live set” recording  
mode, many professional audio interfaces  
go to significant lengths to simulate direct  
hardware monitoring by incorporating a zero-latency  
monitoring engine via dedicated digital signal process-  
ing. This usually requires you to configure a separate  
“virtual” mixer for monitoring. The U.420 ALWAYS  
provides zero-latency monitoring by design, without any  
extra configuration. Hurrah!  
Here are some steps showing how to record a first  
track, and then record additional tracks while monitor-  
ing ones that have already been recorded.  
1. Connect the sound source you wish to record to  
your audio software, for example:  
Due to the nature of its signal path, the U.420 requires  
the use of direct hardware monitoring, as follows:  
A line-level source such as an electronic  
keyboard.  
Arm the track you wish to record onto, on your  
DAW software.  
A turntable connected to the phono inputs.  
An instrument connected directly to the  
instrument input 1 (with the instrument  
switch [11] pressed in).  
On the track you have just armed, press that  
track’s mute button, so that (while recording)  
you do not hear the return of that track com-  
ing from the computer. This will ensure you do  
not mix the direct track you are monitoring,  
with the duplicate of the track on the DAW as  
it is being recorded. You do not want to hear  
the direct and DAW track of the same source  
simultaneously, as the DAW version might be  
slightly delayed, and the combination of the two  
will produce a filtered sound.  
2. Make sure the FW loop switch [21] is not  
pressed in. This will ensure that during each  
recording pass, the audio software only receives  
the track-in-progress as an audio signal, and  
not the pre-existing mix from the computer as  
well.  
3. Set the gain knob  
[12] at the top of the  
Make sure that the DAW’s input meters show  
a healthy level, and if it needs to be increased  
or decreased, adjust the signal’s channel level  
knob [17], not the gain knob [12].  
channel you are using  
to an appropriate  
level for the source  
being recorded, using  
the level set LED  
[10] as a guide. Once  
the gain has been set,  
set the channel level  
[17] to unity (U).  
1
2
LEVEL  
SET  
U
U
GAIN  
-14  
+14  
+10  
+10  
+10  
MAX  
-14  
+14  
+10  
+10  
+10  
MAX  
U
U
U
U
U
U
E
HIGH  
Press record on the DAW and record the track.  
KILL  
KILL  
KILL  
KILL  
KILL  
KILL  
MID  
Overdubbing  
LOW  
To overdub additional tracks while listening to previ-  
ously recorded ones, follow these steps:  
AUX  
The signals going out  
to your computer are  
not affected by the  
main volume knob or  
the phones knob.  
O O  
O O  
Unmute the previously recorded track in the  
DAW. It will now play out of the DAW’s main L-R  
mix into the FW input of the mixer.  
U
U
LEVEL  
O O  
O O  
MAX  
MAX  
Set the level of the FireWire in knob [20]  
to a level where you can hear the previously  
recorded track comfortably.  
Monitoring  
When recording to computer software, there are two  
ways to monitor the track you are recording:  
Arm a new track in the DAW software and mute  
that same DAW channel, and record the new  
track on your DAW *.  
Direct hardware monitoring: Listen to the track  
you are recording directly off of your mixer,  
while also listening to previously-recorded  
tracks on your DAW software, as they are fed  
back into the mixer.  
While recording the new track, you will hear  
the previously recorded tracks coming into the  
mixer’s FireWire input, while you simultane-  
ously hear the current track you are recording  
directly through the mixer hardware.  
”Through-the-DAW” monitoring, where you  
monitor the track you are recording after its  
round trip through the computer software,  
along with any previously recorded tracks.  
Repeat these steps until you have built up all  
the tracks of your recording.  
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* In Tracktion, it is not necessary to mute the output  
of the track you are overdubbing on. Instead, select the  
input to the track (it will be highlighted in red) and dis-  
able the end-to-end function.  
A word about latency (wait-and-see)  
Latency describes the amount of time it takes the  
input signal to pass through the system, and reach  
the output. When recording a guitar and monitoring  
through software, it is the amount of time it takes from  
the moment you strike your guitar string, to the moment  
you hear it in your headphones. You are used to this la-  
tency being very close to zero; when you play your guitar  
through a guitar amp, you hear the signal immediately.  
So when you are recording and monitoring via software,  
you want this latency to be very low.  
We would like to set the latency as low as possible, but  
the smaller it is, the harder the computer will have to  
work. If the latency is very small, the computer needs to  
work very hard to quickly transfer the audio in and out.  
It may not even be able to keep up, especially if there  
are lots of tracks, lots of automation and/or lots of plug-  
ins in your work. If this happens, your audio may stop or  
“drop out.” Drop outs may also occur if you have a slower  
computer or not enough memory.  
You’ll hear existing tracks playing back via the  
FireWire in, and you’ll be monitoring the track you are  
recording through the U.420’s headphones or main out.  
When you play back the recording, you’ll hear the track  
you’ve just overdubbed without un-muting anything.  
Other tips  
One drawback of using direct hardware moni-  
toring (vs. through-DAW monitoring) is that  
the track you are recording will not normally  
be able to take advantage of any effects that  
the DAW’s mixer has to offer, such as a reverb  
on the vocal being recorded, or a guitar amp  
simulation on a directly attached instrument.  
One workaround for this is the following:  
When recording using the overdub method, it is  
important to set the U.420’s latency to it’s lowest oper-  
able setting. This means going into the audio interface  
property page of your recording program and setting the  
latency property to the lowest setting the device and  
your system will accept without any drop-outs, distor-  
tion or CPU overburdening.  
The buffer is an area of computer memory that your  
DAW uses to hold audio as it works. The smaller the  
buffer, the faster audio gets in and out of your com-  
puter, and the lower the latency. The size of the buffer  
is measured in samples. Depending on your system, a  
low setting is typically between 64 and 256 samples. The  
more samples, the higher the latency time value. This  
time value varies by sample rate, as shown in this table.  
Set the latency on your DAW to as low as  
the computer can handle, and set the U.420  
software console panel to the same value  
(see page 25 for more information on the  
console).  
Do not mute the channel on the DAW that  
is being recorded. This will allow you to  
hear a mixture of the direct hardware  
monitor, and the through-DAW signal.  
Samples 44.1 kHz 48 kHz  
96 kHz  
0.7 ms  
1.3 ms  
2.7 ms  
Apply the effect of choice (reverb, amp  
emulation) to the DAW track, which you  
will hear mixed in with the direct hardware  
monitor source.  
64  
1.5 ms  
2.9 ms  
5.8 ms  
1.3 ms  
2.7 ms  
5.3 ms  
128  
256  
As long as the latency is set low enough,  
the timing difference between the direct  
and through-DAW signal should be small  
enough to not cause distraction.  
It is generally accepted that delay or latency times of  
3.3 ms or less, are tolerable for musical timing accuracy.  
Higher latency settings are fine and even necessary  
when in live record or performance mode. The same is  
true for mix-down mode, especially when you start add-  
ing lots of plug-ins.  
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6. The next window reminds you to make sure the  
U.420 is NOT connected to your computer yet.  
Read the instructions and click “Continue.”  
Software installation  
For the PC:  
When using the mixer with a PC, it is necessary to  
first install the drivers and the control panel. The con-  
trol panel allows you to set the sample rate and adjust  
the latency (delay) of the audio passing through the  
mixer’s FireWire interface. Go to page 26 if you use a  
Mac.  
Do not connect the mixer’s FireWire con-  
nector to your computer just yet. We’ll tell  
you when it’s time to do that.  
7. You may get a warning about running the  
installer because it hasn’t passed Windows  
Logo testing. It’s okay. We’ve tested it and it is  
compatible with Windows XP. Click “Continue  
Anyway.”  
To install the software on a PC running  
Windows XP (SPꢀ):  
1. Turn off any (non-essential) applications.  
2. Insert the U.420 CD-ROM into your PC’s CD-  
ROM drive.  
3. Click Start in the task bar, then click Run and  
click Browse. Browse to your CD drive and  
double-click _SETUP.EXE. Then click OK to  
start the installation.  
4. The Installer opens. Click “Continue.”  
8. Now it is time to connect your U.420 FireWire  
connection to your computer. Follow the in-  
structions and then click “Next.”  
5. Next you will see the License Agreement. Read  
through the text and if you are all in favor, click  
“I Agree.”  
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9. Wait until the “Found New Hardware Wizard”  
pops up. Do not select any options, just click  
“Cancel” to continue. If the same screen comes  
back up, click “Cancel” again.  
12. A window will pop up to let you know that the  
installation was successful. Click “Finish.”  
Now you are ready to use the FireWire capabili-  
ties of your U.420.  
Do not worry about the various popup warnings,  
even the one that says “a problem occurred..”  
Pay no attention to the man behind the curtain.  
Console (PC only)  
You should adjust the sample rate and latency from  
within your audio software application, for example in  
Tracktion’s “settings” tab. If this is not an option in your  
software, then use this console instead.  
If you do this from within your software ap-  
plication, do not use the control panel during  
the same session, or there might be a conflict.  
You can use the console for a quick check of the set-  
tings, and to make sure they are the same as your audio  
software settings.  
10. You will get another impertinent warning, this  
time about installing the hardware. It’s okay.  
Click “Continue Anyway.”  
The installer places a shortcut to the console  
on your desktop.  
Adjust the sample rate by clicking on the arrow  
in the sample rate window. (The arrow disap-  
pears if your local software has control.)  
11. The drivers and control panel will be installed  
on your computer.  
Adjust the latency by clicking and moving the  
slider in the display.  
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For the Mac:  
Selecting the device (Mac/PC):  
1. If you have followed the preceeding instruc-  
tions for the PC or Mac, connect the U.420 to  
your computer using the FireWire connection.  
Macintosh OS X Audio MIDI Setup  
(version 10.ꢁ.9 or later):  
2. In your audio production software, such as  
Tracktion, select the U.420 as your input and  
output device. The screenshot below shows the  
“Settings” area of Tracktion 3.  
Macintosh OS X does not require FireWire drivers  
to be installed. OS X provides a dedicated setup utility  
for audio and MIDI. You can use the Audio MIDI Setup  
utility to change the default audio input and output and  
general system settings on your Macintosh.  
1. Go to the Applications folder and open the  
Utilities folder.  
2. Double-click “Audio MIDI Setup.”  
3. Play a source into the U.420 and verify that your  
software is receiving the signals correctly.  
4. Record audio and play it back to verifiy every-  
thing is working nicely.  
3. Click the Audio Devices tab, and select U.420 in  
the “Properties For” drop-down box.  
4. Here you can see the settings for the U.420. You  
can also choose the U.420 as your default input  
or output, as well as designate it to be used for  
the system sound output.  
5. You’re ready to go with any Mac OS X Core  
Audio host application (i.e., Tracktion, Logic,  
Cubase, Nuendo, Live, Digital Performer, etc.).  
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U.420 Limited Warranty  
Please keep your sales receipt in a safe place.  
IMPORTANT: Make sure that the Service Request Number  
is plainly written on the shipping carton. No receipt, no  
warranty service.  
A. LOUD Technologies Inc. warrants all materials,  
workmanship and proper operation of this product for a period  
of one year from the original date of purchase. You may  
purchase an additional 24-month Extended Warranty (for a  
total of 36 months of coverage). Visit our website and follow  
If any defects are found in the materials or workmanship or  
if the product fails to function properly during the applicable  
warranty period, LOUD Technologies, at its option, will repair  
or replace the product. This warranty applies only to equipment  
sold and delivered within the U.S. and Canada by LOUD  
Technologies Inc. or its authorized dealers.  
E. LOUD Technologies reserves the right to inspect any  
products that may be the subject of any warranty claims before  
repair or replacement is carried out. LOUD Technologies may,  
at our option, require proof of the original date of purchase in  
the form of a dated copy of the original dealer’s invoice or sales  
receipt. Final determination of warranty coverage lies solely  
with LOUD Technologies.  
F. Any products returned to one of the LOUD Technologies  
factory-authorized service centers, and deemed eligible  
for repair or replacement under the terms of this warranty  
will be repaired or replaced. LOUD Technologies and its  
authorized service centers may use refurbished parts for repair  
or replacement of any product. Products returned to LOUD  
Technologies that do not meet the terms of this Warranty  
will not be repaired unless payment is received for labor,  
materials, return freight, and insurance. Products repaired  
under warranty will be returned freight prepaid by LOUD  
Technologies to any location within the boundaries of the USA  
or Canada.  
B. For faster processing, register online at www.mackie.com,  
or you may fill out and mail in the product registration card  
included along with this manual.  
C. Unauthorized service, repairs, or modification of Mackie  
products will void this warranty. To obtain repairs or replacement  
under warranty, you must have a copy of your sales receipt from  
the authorized Mackie dealer where you purchased the product.  
It is necessary to establish purchase date and determine whether  
your Mackie product is within the warranty period.  
D. To obtain warranty repair or replacement:  
G. LOUD Technologies warrants all repairs performed  
for 90 days or for the remainder of the warranty period.  
This warranty does not extend to damage resulting from  
improper installation, misuse, neglect or abuse, or to exterior  
appearance. This warranty is recognized only if the inspection  
seals and serial number on the unit have not been defaced or  
removed.  
1. Call Mackie Technical Support at 800/898-3211, 7 AM  
to 5 PM Monday through Friday (Pacific Time) to get  
authorization for repair or replacement. Alternately, go to  
support), and follow the instructions for reporting a warranty  
issue and submitting a request for an advance replacement.  
2. Advance Replacement: Mackie will ship a replacement  
unit to you along with an invoice for the suggested  
retail price of the replacement unit. You must return the  
defective unit immediately to cancel the invoice. If you do  
not return the defective unit within 30 days, you must pay  
the full amount stated in the invoice to satisfy your debt.  
H. LOUD Technologies assumes no responsibility for the  
timeliness of repairs performed by an authorized service  
center.  
I. This warranty is extended to the original purchaser. This  
warranty may be transferred to anyone who may subsequently  
purchase this product within the applicable warranty period  
for a nominal fee. A copy of the original sales receipt is  
required to obtain warranty repairs or replacement.  
3. Repair: When you call Mackie Technical Support,  
explain the problem and obtain a Service Request  
Number. Have your Mackie product’s serial number  
ready. You must have a Service Request Number before  
you can obtain factory-authorized service.  
J. This is your sole warranty. LOUD Technologies does not  
authorize any third party, including any dealer or sales  
representative, to assume any liability on behalf of LOUD  
Technologies or to make any warranty for LOUD Technologies  
Inc.  
• Pack the product in its original shipping carton. Also  
include a note explaining exactly how to duplicate the  
problem, a copy of the sales receipt with price and date  
showing, your daytime phone number and return street  
address (no P.O. boxes or route numbers, please!), and  
the Service Request Number. If we cannot duplicate the  
problem or establish the starting date of your Limited  
Warranty, we may, at our option, charge for service time  
and parts.  
K. THE WARRANTY GIVEN ON THIS PAGE IS THE SOLE  
WARRANTY GIVEN BY LOUD TECHNOLOGIES INC.  
AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESS  
AND IMPLIED, INCLUDING THE WARRANTIES OF  
MERCHANTABILITY AND FITNESS FOR A PARTICULAR  
PURPOSE. THE WARRANTY GIVEN ON THIS PAGE SHALL BE  
STRICTLY LIMITED IN DURATION TO ONE YEAR FROM THE  
DATE OF ORIGINAL PURCHASE FROM AN AUTHORIZED  
MACKIE DEALER. UPON EXPIRATION OF THE APPLICABLE  
WARRANTY PERIOD, LOUD TECHNOLOGIES INC. SHALL  
HAVE NO FURTHER WARRANTY OBLIGATION OF ANY  
KIND. LOUD TECHNOLOGIES INC. SHALL NOT BE LIABLE  
FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL  
DAMAGES THAT MAY RESULT FROM ANY DEFECT IN THE  
MACKIE PRODUCT OR ANY WARRANTY CLAIM. Some states  
do not allow exclusion or limitation of incidental, special, or  
consequential damages or a limitation on how long warranties  
last, so some of the above limitations and exclusions may not  
apply to you. This warranty provides specific legal rights and  
you may have other rights which vary from state to state.  
• Ship the product in its original shipping carton,  
freight prepaid to the authorized service center. Write  
the Service Request Number in BIG PRINT on top of  
the box. The address of your closest authorized service  
center will be given to you by Technical Support, or it  
may be obtained from our website. Once it’s repaired,  
the authorized service center will ship it back by ground  
shipping, pre-paid (if it qualified as a warranty repair).  
Note: Under the terms of the warranty, you must ship  
or drop-off the unit to an authorized service center.  
The return ground shipment is covered for those units  
deemed by us to be under warranty.  
Note: You must have a sales receipt from an authorized  
Mackie dealer for your unit to be considered for  
warranty repair.  
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Owner’s Manual  
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16220 Wood-Red Road NE • Woodinville, WA 98072 • USA  
United States and Canada: 800.898.3211  
Europe, Asia, Central and South America: 425.487.4333  
Middle East and Africa: 31.20.654.4000  
Fax: 425.487.4337 • www.mackie.com  
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